The truck runs for a few seconds and shuts off, low fuel pressure?

LOUIELOUIE22

MEMBER
2000 FORD F-150
4.6L
V8
4WD
AUTOMATIC
87,000 MILES

Replaced fuel pump two years ago put about 1,000 miles since then. Now the truck runs for a few seconds and shuts off. I connected a pressure gauge to the rail and got about 4 pounds of pressure with the fuel relay bypassed. This truck does not have a fuel pump driver module and I do not know how the fuel pressure gets regulated. The fuel pump draws 3 amps when fuel relay is bypassed, and the pressure gauge remains at 4 pounds. I am stuck and need help.

Friday, June 14th, 2024 AT 7:15 AM

1 Reply

TY ANDERSON

MECHANIC
719 POSTS

Fuel pressure should be between 35-45 PSI with the key on, engine off or 28-50 PSI with the engine running. This is definitely a fuel problem.
Here are some possible causes for your low fuel pressure: Clogged fuel filter, bad fuel pump, Bad fuel pressure regulator, Stuck open fuel injector, or a circuit issue with the fuel pump (fuel pump relay, wiring and electrical connections).
Fuel system pressure is regulated at the pressure regulator on the fuel rail by the fuel injectors. There's a vacuum hose that connects to it also.
Ford does have a history of having issues with the fuel inertia cut off switch causing fuel delivery problems. Sometimes tapping this switch with the end of a screwdriver will aggravate the circuit making it worse or work better. You could bypass this switch altogether to test if it gets better. Don't leave it bypassed though. This switch is located behind the kick panel area on the passenger side footwell under the dashboard.
Let us know what you find or if you have any other questions.

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Friday, June 14th, 2024 AT 9:08 AM